#include <iostream>
#include <deque>


int main()
{
    std::deque<int> d;

    d.push_back(1);
    d.push_back(2);
    d.push_back(3);

    d.push_front(99);
    d.pop_front();
    for(auto ite = d.begin(); ite != d.end();ite++)
    {
        std::cout<<*ite<<" ";
    }
    std::cout<<std::endl;
    return 0;
}